1. Field of the Invention
Embodiments of the present invention generally relate to a free standing structure such as a switch or cantilever and a method of moving the free standing structure between high and low adhesion states.
2. Description of the Related Art
As the size of semiconductor devices continues to shrink, so does the size of micro-electromechanical (MEMS) devices that are coupled to the semiconductors. MEMS devices may be used as miniature relay switches, capacitance switches, non-volatile memory elements and for many more applications. The MEMS devices have a switch or cantilever that moves between at least two positions to either permit or deny a current from flowing through the switch. In other MEMS devices the cantilever moves between being in contact with a landing electrode to not being in contact. In some of these devices no current flows, but a change in the capacitance of the landing region occurs.
MEMS devices are made using similar processing steps to those found in semiconductor foundries and therefore can be manufactured cost effectively on a wafer scale. One of the issues found in shrinking MEMS devices to the scale of less than a few micrometers is that the adhesion forces begin to be large in comparison to other restoring forces in the devices. These restoring forces are usually the spring restoring force of the MEMS device itself or electrostatic forces used to pull the MEMS device out of intimate contact with a substrate, for the case of a simple cantilever. The adhesion forces depend on the surface chemistry, but include van der Waals forces, electrostatic forces from fixed charges, covalent bonding and metal-metal bonding for the case of two conducting surfaces. Once the adhesion forces become larger than the restoring forces, the device may undesirably remain in contact with the substrate.
Therefore, there is a need in the art for a method of overcoming adhesion forces in MEMS devices.